Javax, @Defaultvalues, @Prepersistent, @Preupdate

Question

I’m learning to play with Javax, and persistence of Java and I want to know if there’s any way to leave a default value for the database.

Example in SQL:

variacao TIMESTAMP DEFAULT CURRENT_TIMESTAMP

How would I do that in my Template code ?

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name="id")
private int id;

@NotNull
@Column(name="nota")
private int nota;

@NotNull
@Column(name="data")
private Timestamp data;

@Column(name="comentario")
private String comentario;

@Column(name="evento_id")
private Evento evento_id;

@Column(name="pessoa_id")
private Pessoa pessoa_id;

1) What is the difference between the following items? a) @Defaultvalues b) @Prepersistent c) @Preupdate

2) And which one would I use for this case ? a) @Defaultvalues b) @Prepersistent c) @Preupdate

Answer 1

From what I understand you are using JPA, in this case prefer to let the default value be generated by the bank use so:

@Column(name = "DATA_ATUALIZACAO", columnDefinition = "TIMESTAMP DEFAULT CURRENT_TIMESTAMP")

This will only work if you let JPA create the tables, or export the table creation script.

1) What is the difference between the following items?

@Prepersist

Callback is executed before the entity is persisted.

@Preupdate

Callback runs before the entity is updated.

2) And which one I would use for this case ?

This will depend on the purpose of your column, for example:

• If your column DATE you to store the registration date would have to use @PrePersist;

• If your column DATE you to store the update date would have to use @PreUpdate;

See [Hibernate] which is one of JPA implementations: https://docs.jboss.org/hibernate/orm/4.0/hem/en-US/html/listeners.html